Lateral Branch Blocks
for Sacroiliac Joint Pain
A sacroiliac (SI) joint injection—also called a sacroiliac joint block—is primarily used either to diagnose or treat low back pain and/or sciatica symptoms associated with sacroiliac joint dysfunction.
The sacroiliac joints lie next to the spine and connect the sacrum with the hip on both sides. There are two sacroiliac joints, one on the right and one on the left. Joint inflammation and/or dysfunction in this area can cause pain.
The purpose of a sacroiliac joint injection is two-fold: to diagnose the source of a patient’s pain, and to provide therapeutic pain relief. At times, these are separated and a patient will undergo a purely diagnostic or therapeutic injection, although often the two are combined into one injection.
A diagnostic SI joint injection is used to confirm a suspected diagnosis of sacroiliac joint dysfunction. This is done by numbing the sacroiliac joint with local anesthetic (e.g. lidocaine). The injection is performed under fluoroscopy (X-ray guidance) for accuracy. Once the needle has entered the sacroiliac joint, contrast is injected into the joint to ensure proper needle placement and proper spread of medication. The numbing medication is then injected into the joint.
After the numbing medication is injected, the patient is asked to try and reproduce the pain by performing normally painful activities. If the patient experiences 75-80% pain relief for the normal duration of the anesthetic, a tentative diagnosis of SI joint dysfunction is made. A second diagnostic sacroiliac injection should be performed using a different numbing medication (e.g. Bupivicaine) in order to confirm the diagnosis.
If this second diagnostic injection also provides 75-80% pain relief for the duration of the anesthetic, there is a reasonable degree of medical certainty the sacroiliac joint is the source of the patient’s pain.
Lateral Branch Blocks
Lateral branch blocks may be performed to diagnose SI joint pain. The lateral branch nerves are small nerves that branch off the sacral spinal nerves and provide sensation to the joint. A lateral branch block might be performed to determine if a patient is a candidate for a radiofrequency nerve ablation to provide longer lasting relief of the pain associated with SI joint dysfunction.